This invention relates generally to electricity metering and more particularly, to an electronic electricity meter configurable to compensate for temperature of the meter.
Electronic electricity meters operate in various environments to measure and record energy consumption. For example, electricity meters are often installed on the outside of a customer""s structure to allow easy access to the meter. As a result, components of the meter are exposed to temperature changes caused by the weather. In order to accurately measure the amount of energy consumed by the customer, the internal components of the meter must have high accuracy and low sensitivity to temperature changes.
These low temperature coefficient components maintain the accuracy of the meter despite the temperature variations of the environment. Using such low temperature coefficient components, however, increases the cost of the electricity meter.
It would be desirable to provide a meter which automatically compensates energy consumption measurements for temperature changes so that higher temperature coefficient components can be used in the meter.
These and other objects may be attained by an electricity meter which, in one embodiment, includes a temperature sensing unit for generating a signal representative of the temperature within the meter. The electricity meter further includes a current sensor, a voltage sensor and a processing unit connected to the outputs of the current sensor, the voltage sensor and the temperature sensing unit.
In operation, the processing unit samples the analog output signals from the current sensor and the voltage sensor to determine a line current signal and a line voltage signal. The processing unit also samples the output of the sensing unit. If the temperature signal is within a valid range, the processing unit adjusts the line current and line voltage signals for temperature characteristics based on the temperature representative signal. The adjusted line current and line voltage signals are then utilized within the processing unit to determine the adjusted energy consumption of the load.
If the temperature representative signal is outside the valid range, the processing unit does not adjust the line current and line voltage signals and the energy consumption is determined using the line current and line voltage signals with no temperature adjustment. If the temperature signal is outside the valid range, such condition may mean that the temperature sensing unit is not properly operating.
The above-described meter provides a temperature sensing unit which measures the meter temperature inside the meter so that the line current and line voltage signals may be adjusted to compensate for the temperature characteristics of the meter. Such adjustment for the temperature characteristics of the meter enables use of higher temperature coefficient components, therefore reducing the cost of the meter.